<select name="log_comb" style="width: 130px">
    <option value="With aditive" <?php if ($log_comb == 'With aditive') { echo "selected"; } ?>>With aditive</option>
    <option value="Without aditive" <?php if ($log_comb == 'Without aditive') { echo "selected"; } ?>>Without aditive</option>
</select>